This invention relates in general to boilers, and, in particular, to an electrode assembly for use in electric boilers.
More specifically, but without restriction to the particular use which is shown and described, this invention relates to an improved electrode for an electric boiler, employing a forced water flow about the electrode periphery to minimize the formation of gas bubbles.
In one well known form of boiler for heating water and producing steam, an electrical current is directed from one or more electrodes through surrounding water to generate heat. The generated heat raises the water temperature to a predetermined level in the case of hot water boilers, and converts the water into steam in steam boilers. One type of electric boiler of the prior art employs a neutral shield in conjunction with the electrode causing the maximum voltage gradient to occur at the surface of the electrode. If the voltage gradient at the electrode surface is high or equal to the breakdown voltage of the water contained in the boiler, then arcing may occur. Arcing erodes the electrode surface to affect adversely its length of service. Generally, arcing associated with the formation of maximum voltage, can be alleviated by properly selecting the size of the electrode and the neutral shield in relation to the boiler water conductivity, breakdown voltage, power output, and supply voltage.
In addition to the maximum voltage gradient forming at the electrode surface, severe arcing may also arise when steam bubbles are formed on or adjacent the surface of the electrode. Since steam has a much greater electrical resistivity compared to water, the formation of steam bubbles can arrest most of the voltage between the electrode and neutral shield and seriously interfere with the operation of the boiler itself. When the voltage difference across the steam bubbles is equal to or higher than the breakdown voltage, detrimental arcing will take place across the bubble. The electrodes utilized in prior art electric boilers have been highly ineffective in eliminating or removing the steam bubbles from the electrode surface for prevention of the arcing problem.